Hand-stopping is accomplished by pushing the right hand into the bell. Hand-starting, of course, depends on pulling the hand out of the bell. However, it takes considerable preparation to hand-start your horn successfully. Here is how I start my Geyer-model horn.
1. Undo the string or metal strut linking the thumb key with the B flat rotor.
2. Tinker with the corks and fittings, etc, until the rotor can be turned through a complete circle.
3. Take a six-foot length of string (I use the same kind of string to link the finger keys with the valve rotors) and drop it down the bell until one end of the string engages the port of the B flat rotor.
4. Spin the rotor six times clockwise with your left hand. This causes the string to wind around the rotor. You should feel the string tugging your right hand in the bell. Don't let go!
5. Place a drop of bearing oil and a drop of kerosene on the upper bearing plate of the B flat rotor.
6. Attach the positive terminal of your type A battery to the upper bearing ferrule, and ground the other end on your bell. (Low players may prefer a type AA battery.)
7. Pull the string briskly out the bell. Congratulations! You have just hand-started your horn. If the rotor is not spinning at exactly 440 Hz (or 220 Hz if you used a type AA battery), you may fine-tune it through judicious adjustment the position of your right hand.
8. Detach the battery. Your B flat rotor should be turning counterclockwise, unless your horn was manufactured in the southern hemisphere.
It is generally not advisable to hand-start your horn while playing. The powerful suction at the mouthpipe venturi might damage your embouchure.
I have never played a Vienna horn; the action in these is reciprocating, rather than rotatory. They are probably as hard to start as Schmidt-model horns.
Some players prefer to use cranks to start their horns for them. Others go so far as to attach the cranks to an electric drill. Such artificial devices are inauthentic, and not in keeping with the true spirit of horn playing. I like to think that those who read the hornlist have learned not to pay any attention to cranks.
Gotta go,
Cabbage